Fat is an important constituent of frozen aerated confections such as ice cream. Fats are largely made up of triglycerides (approximately 98%), together with minor amounts of other components such as phospholipids and diglycerides. Triglycerides are esters of glycerol with three fatty acids, which may be the same or different. Fatty acids which have no carbon-carbon double bonds are said to be saturated (herein abbreviated as SAFA), whereas fatty acids that contain one or more carbon-carbon double bonds are said to be unsaturated.
The conventional manufacturing process for frozen aerated confections consists of a number of steps: (i) mixing the ingredients, (ii) pasteurisation and homogenisation, (iii) ageing, (iv) aerating and partially freezing the mix, (v) extrusion from the freezer, and (vi) hardening. This process is described in detail in, for example, Arbuckle, W. S., Ice Cream, 4th Edition, AVI publishing 1986, chapters 11-13. In the ageing step, the mix is held at a low temperature, typically 4° C., for a period of time, typically a few hours. One purpose of the ageing step is to allow time for the fat (which is liquid at the pasteurization temperature) to crystallize before the mix is frozen and aerated. Traditionally, frozen aerated confections such as ice cream have been prepared with fats having a high proportion of saturated fat, for example dairy fat (60-70%) or coconut oil (>90%). Saturated fats are used because they crystallise relatively easily during the ageing step so that most of the fat is solid during freezing and aeration. This is important because the presence of solid fat results in ice cream that can be aerated uniformly and consistently, retains its shape after extrusion and has a good texture when eaten. Shape retention is a critical factor in producing some product formats, for example Viennetta™. Such products cannot normally be produced with a low level of solid fat.
Consumers are now looking for frozen aerated confections which have all the properties of these traditional products but which are healthier. One concern that consumers have is that eating saturated fats increases the low density lipoproteins (LDL) in their circulation. Increased LDL levels are believed to be associated with increased risk of coronary heart disease and stroke. Replacing the saturated fats in the diet with unsaturated fats has been proposed as one way to reduce the amount of potentially harmful LDLs in the blood.
Ice creams made with fats having SAFA levels lower than those of dairy fat are known. JP 55/153561 describes the use of the medium-melting fraction of palm oil to produce ice cream which has similar palatability and melting properties in the mouth to ice cream based on milk fat. However, the SAFA contents relatively high and the problem of reducing the SAFA content is not addressed.
Attempts have also been made to produce frozen aerated confections using fats with low saturated fatty acid contents. However, it is difficult to design low SAFA fats for frozen aerated confections because a number of different interacting criteria must be satisfied simultaneously. Simply replacing saturated fats with unsaturated fats provides the health benefit, but at the expense of the processability and texture of the confection because unsaturated fats do not contain sufficient solid fat. JP 57/036944 describes the production of ice cream with oils that are very low in SAFA, such as safflower oil and sunflower oil. To overcome the problem of producing good ice cream with liquid fat, it was found necessary to use a special emulsifier in the form of a sucrose fatty acid ester. However, such additives can detract from the attractiveness of the product to consumers.
There is a need therefore to provide low SAFA fats for use in frozen aerated confections which give good processing properties (such as aeration and shape retention on extrusion) and good texture for the consumer, but do not require other additives, such as sucrose fatty acid esters.